There is very little science to those expiration dates and so I imagine that they are fine to use. The manufacturers have their own economic interest in putting short expiration dates. The same is true of cold medicines. In fact this has been the subject of some congressional inquiry. They won't make a child sick. the only issue is whether all the nutrients are quite as potent as they were. Shelf life is not a cliff. Something ages over time. The process of aging and losing nutrients is very gradual. So if you have something that expires on March 31, it doesn't switch to being bad on April 1. What you have in your house is something that was made last year and has been aging ever since. Also, if your children are over 1, they can move to whole milk. The benefit of the next step products is not proven at all and it is expensive.